It is known that, if foreign matter such as thrombi or emboli choke a blood vessel such as a coronary artery of the heart, then it obstructs the flow of the blood and causes a serious disorder. One known catheter assembly for sucking such a thrombus as described above is disclosed in U.S. Pat. No. 5,569,204.
The catheter assembly disclosed in U.S. Pat. No. 5,569,204 includes three catheters combined, namely a central catheter, a dilator provided on the inner side of the central catheter, and an outside catheter provided on the outside of the central catheter. After the catheter assembly reaches a target location, the dilator is pulled out, and a thrombus and so forth are sucked and removed through the lumen of the central catheter by a suction device connected to the proximal end of the central catheter. Further, with the catheter assembly disclosed in U.S. Pat. No. 5,569,204, if a thrombus or the like chokes the central catheter, then the central catheter is pulled out, and the pulled out central catheter is washed or a new central catheter is prepared and inserted into the outside catheter, or after the choked central catheter is pulled out, suction is performed using the outside catheter.
The catheter assembly of U.S. Pat. No. 5,569,204 having such a configuration as described above makes use of the lumen of the central catheter or the outside catheter as a suction path for the suction. The inner diameter of the lumen of each of the catheters has a constant dimension from the distal end to the proximal end, and the inner diameter cannot avoid being restricted by the finest portion of the blood vessel into which the catheter assembly is inserted. The finest portion of the blood vessel is usually an extremity position into which the catheter assembly is inserted.